UHF radio control for submarines (openLRS, LoRa, FSK etc. on 458Mhz and 433Mhz )

Another test of the LoRa system in my Turkish Nordenfelt model. I am quite happy with the system now and I will use it as my control system "of choice" from now on. (With openLRS used occasionally.)

It has quite high latency but this is OK for submarine models, I think. I like the telemetry (battery voltage is so useful if you are using Lipos) and the failsafes (set in software.) The range (including submerged) is very adequate.

The latest version of the software continues to send telemetry every 10 seconds even if the TX is off. This does perhaps enable lost model direction finding and location (in addition to ultrasonic Pinger use) with my foldable Yagi antenna used some months ago:



The software (Current versions LoRa-Rhead-RX-3.4  & Lora-Rhead-TX-2.7) is here:

https://github.com/rdforrest/LoRa-TX-RX-Test-458MHz








Dived with just the funnel showing!



Dived with just the funnel showing! (Typically murky water)



The TX setup installed in a (fairly roomy) 3D printed box:
The oLED display cycles through the three telemetry values. (This shows the RSSI)



This shows battery voltage:






Two TX/RX sets of equipment (fairly easy to assemble by the informed DIY builder) They all use the Adafruit RFM96W breakout board which is easier to connect to than a bare chip and has level convertors for the 5v used in the Arduino Nano:



Perhaps not the most exciting set of videos but they show the range you can expect together with demonstrations of diving etc.

https://youtu.be/1oW9hinyQcs

https://youtu.be/EuwLlZFAwpA

https://youtu.be/5Jb61F0cMoo

https://youtu.be/q9l2JEAQ9Qo

https://youtu.be/XgTsew0UZwo

So, my update on the ImmersionRC ezuhf equipment...

not worth the bother for me.

I spent the weekend of septermber 4th & 5th 1250 miles from home at a Mare Island Fun Run in "lovely" San Francisco. I took 3 submarines with me, my trusty Norbert Bruggen Delta, a Small World Models 1/96 scale Blueback (1970s era US diesel sub) and a 1/32 scale 1903 Holland. the holland and blueback were using the FrSky 915mhz equipment, and the delta was using the ezuhf equipment.

all three ran equally well in identical conditions.


One thing that was very interesting to me.

One of the local Mare Island club members was using a FrSky qX7 transmitter with a 75mhz futaba module.

https://store.flytron.com/products/turnigy-x9-futaba-module-adapter-v3

he simply wired up an old 75mhz antenna to the appropriate pin on the module, plugged the module into the adapter, plugged the adapter into the socket on the back of the transmitter, and made a bracket to mount the antenna on the transmitter, he set the protocol for the module to PPM, and everything ran as expected.

Very interesting observation Tim.

Does that mean that the Futaba modules use a standard PPM signal as input?

In which case anyone with  a 75mHz or 40 Mhz* module could plug it into the trainer plug of any TX?

Could be very useful for a lot of folks.

David

* for the UK. When last I looked they were expensive and hard to find.

david f wrote:Very interesting observation Tim.

Does that mean that the Futaba modules use a standard PPM signal as input?

In which case anyone with  a 75mHz or 40 Mhz* module could plug it into the trainer plug of any TX?

Could be very useful for a lot of folks.

David

* for the UK. When last I looked they were expensive and hard to find.

David, yes, the protocol selected when using the 75mhz (or 40mhz) modules would be ppm...  and the use of a trainer port instead might add additional "needs"  (some trainer ports invert the signal, and some require the use of a "trainer switch" to indicate who has control of the rf deck, student or instructor)...

and yes, here in the states, the 75mhz modules are impossible to find, and expensive...  but for someone that already has a drawer full of them...

I joined this forum after reading about your issues using openlrs. im probably one of the handful of people that originally used openlrs on 458mhz. Openlrs has potential for very long range and signal penetration but it has to be configured for it, the main issues i could see you having is

1. antennas, the stock openlrs antennas are rubbish and are only useful for indoor testing. make a 1/4 wave dipole using some wire or coax. you need one for both the transmitter and receiver. 433mhz antennas wont be correctly tuned, so you need an antenna that is slightly shorter to compensate for the higher frequency.

2. Air data rate, openlrs has 2 data rates in the settings, one is for the serial port and one is for the transmission rate. out the box this is set quite high as its also used for a telemetry link but since your not using a flight control system you dont need the bandwidth or the low latency so you should drop the transmission rate down to 9600 or 4800 and also reduce the number of channels to 4+4 (4 high resolution channels + 4 low resolution channels) to minimize data usage minimizing the latency. by reducing the transmission rate you more than double the range and it shouldn't effect your FRSKY D based telemetry since it doesn't use much data.

you should also look at the Beacon function of the openlrs recevier, basically if it doesn't receive a packet from the handset it will start transmitting a tone on fixed frequency lowering the power level with each pulse so you can use the RF signal to tell if your getting closer or not. this was tested to 100+ miles in open air using a baufang radio, but it should still work to a decent depth, as the signal required is much weaker than needed for a data link.


openlrs has something called channel relay mode so you can use the servo pins to directly turn signals off and on, so you can just use a opto-isolated relay to run systems.

Gents,

I have been aware of another manufacturer of the UHF equipment for quite some time, but until recently, their equipment has been too expensive for my tastes.

well, they now have a v2 set of hardware, which is now priced within my budget, so i have ordered a set.  it is the classic TX module built to fit into the JR style socket (found on many transmitters, such as FrSky and FlySky).  the set has arrived, and as before, i will be putting them into my tried and true Delta to see how well they work.

these new items are not 433/458 mhz,  they are 915mhz (USA) or 868mhz (EU)

see links for what i purchased.


tx module:
https://www.team-blacksheep.com/products/prod:crossfire_micro_tx


rx and pwm adapter (allows the drone-esque receiver to use standard servos)
https://www.team-blacksheep.com/products/prod:xf_nano_div_rx
https://www.team-blacksheep.com/products/prod:nano_divrx_adptr


as i stated, i have already received these three items, and have wired them up (soldered servo adapter to receiver) tested them, and now get to install them in a sub for testing.

the adapter gives the receiver the ability to work with 8 standard size servos, and the system also returns telemetry data, and since the receiver is a "diversity" receiver (two rf decks)  i actually get two separate RSSI signals plus receiver battery voltage as a minimal set of data.  I am also looking into seeing what other telemetry data can be collected, i will let you all know what i find as i progress.

tsenecal wrote:Gents,

I have been aware of another manufacturer of the UHF equipment for quite some time, but until recently, their equipment has been too expensive for my tastes.

well, they now have a v2 set of hardware, which is now priced within my budget, so i have ordered a set.  it is the classic TX module built to fit into the JR style socket (found on many transmitters, such as FrSky and FlySky).  the set has arrived, and as before, i will be putting them into my tried and true Delta to see how well they work.

these new items are not 433/458 mhz,  they are 915mhz (USA) or 868mhz (EU)

see links for what i purchased.


tx module:
https://www.team-blacksheep.com/products/prod:crossfire_micro_tx


rx and pwm adapter (allows the drone-esque receiver to use standard servos)
https://www.team-blacksheep.com/products/prod:xf_nano_div_rx
https://www.team-blacksheep.com/products/prod:nano_divrx_adptr


as i stated, i have already received these three items, and have wired them up (soldered servo adapter to receiver) tested them, and now get to install them in a sub for testing.

the adapter gives the receiver the ability to work with 8 standard size servos, and the system also returns telemetry data, and since the receiver is a "diversity" receiver (two rf decks)  i actually get two separate RSSI signals plus receiver battery voltage as a minimal set of data.  I am also looking into seeing what other telemetry data can be collected, i will let you all know what i find as i progress.

TBS crossfire has been around for a while but your going to run into issues if you want to use it legally, specifically 868mhz is not recognized by ofcom as being allowed for RC model control, it can be used for telemetry if the maximum transmitter power is only 10mw, thats 1/10th of the power allowed on 2.4ghz  given that the frequency is only 3x lower your going to end up with about the same range or slightly less than a regular 2.4ghz system. with 458mhz its 5x lower than 2.4ghz at the same power level of 100mw giving you the extra range and penetration. the uk has different radio laws from the rest of the eu, that's why its technically legal everywhere else apart from in the uk lol.

Realistically it doesn't matter, no one cares how much power you put out, it won't effect anything. its just something I had to look a lot into as I used to design commercial drone aircraft so everything had to be totally legal to go past the CAA. it had to have RF test certificates to show it was compliant.


https://www.ofcom.org.uk/__data/assets/pdf_file/0028/84970/ir-2030.pdf

Just a reminder that Tim is in the USA and I think you must be in the UK?
David

david f wrote:Just a reminder that Tim is in the USA and I think you must be in the UK?
David

yes my mistake.

GeoFrancis,

no worries, i am in the USA, and hopefully, this forum has an international audience, so both your info and my info is useful.

tsenecal wrote:GeoFrancis,

no worries, i am in the USA, and hopefully, this forum has an international audience, so both your info and my info is useful.

The TBS module can put out 2W when powered by an external power source, so that is a lot of power at a relatively low frequency. It's got half the penetration of 433/458 but with that much power it doesn't really matter, I suspect you will be able to go as deep as you want.

other issues you could run into are:

dynamic transmitter power is determined by the receiver RSSI sent back, the problem is the receiver is only sending back at 100mw so as soon as it looses telemetry it goes to max power. so it works dynamically up to around 100mw then just goes to full power. I found it was a bit overly sensitive, and would max power with the slightest thing so your probably better just setting it to something like 500mw and leaving it there.

2W of rf power tends to cause problems for other devices, jamming other receivers in close proximity FPV video receivers and GPS are the most effected but its usually only within 5m or so.

Line-up at the lake in Barrow this Sunday.
David Jacques newly finished DEEP DIVE VII sailing and diving well on its first outing.
Interesting that this model and the Charlie class are both operating on 458 MHz openLRS (for the Deep Dive) and LoRa (For the Charlie Class) - both without any interference problems,